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*Memos:
- explains variable assignment.
- explains iterable unpacking in variable assignment.
- explains * for iterable unpacking in function.
- explains ** for dictionary unpacking.
- explains *args and **kwargs in function.
You can use * for iterable unpacking in a variable assignment as shown below:
*Memos:
- A * is an iterable unpacking operator.
- A *variable can store zero or more values as a list in a variable assignment.
- Only one *variable can be used in each expression of the left side of a variable assignment.
- Zero or more *iterables can be passed to a function with the zero or more values unpacked from zero or more iterables.
*v1, v2, v3 = [0, 1, 2, 3, 4]
*v1, v2, v3 = (0, 1, 2, 3, 4)
v1, v2, *v3 = [0, 1, 2, 3, 4]
v1, *v2, v3 = [0, 1, 2, 3, 4]
v1, *v2, v3 = [0, 1, 2, 3]
v1, *v2, v3 = [0, 1, 2]
v1, *v2, v3 = [0, 1]
# No error
*v1, v2, *v3 = [0, 1, 2, 3, 4]
# SyntaxError: multiple starred expressions in assignment
v1, *v2, v3 = [0]
# ValueError: not enough values to unpack (expected at least 2, got 1)
*v1, = []
*v1, = 5, # Tuple
*v1, = (5,)
# No error
*v1, = [0, 1, 2]
*v2 = *v1 # SyntaxError: can't use starred expression here
*v1 = [] # SyntaxError: starred assignment target must be in a list or tuple
*v1, = 5 # TypeError: cannot unpack non-iterable int object
*v1, v2, v3 = [0, 1, 2, 3, 4]
*v1, v2, v3 = (0, 1, 2, 3, 4)
print(v1, v2, v3) # [0, 1, 2] 3 4
print(*v1, v2, v3) # 0 1 2 3 4
v1, v2, *v3 = [0, 1, 2, 3, 4]
print(v1, v2, v3) # 0 1 [2, 3, 4]
print(v1, v2, *v3) # 0 1 2 3 4
v1, *v2, v3 = [0, 1, 2, 3, 4]
print(v1, v2, v3) # 0 [1, 2, 3] 4
print(v1, *v2, v3) # 0 1 2 3 4
v1, *v2, v3 = [0, 1, 2, 3]
print(v1, v2, v3) # 0 [1, 2] 3
print(v1, *v2, v3) # 0 1 2 3
v1, *v2, v3 = [0, 1, 2]
print(v1, v2, v3) # 0 [1] 2
print(v1, *v2, v3) # 0 1 2
v1, *v2, v3 = [0, 1]
print(v1, v2, v3) # 0 [] 1
print(v1, *v2, v3) # 0 1
*v1, = [0, 1, 2]
print(v1) # [0, 1, 2]
print(*v1) # 0 1 2
*v1, = []
print(v1) # []
print(*v1) # Nothing
*v1, = 5, # Tuple
print(v1) # [5]
print(*v1) # 5
*By default, only keys are assigned to variables from a dictrionary same as using .
*v1, v2 = {'name":"John", "age":36, "gender":"Male"}
*v1, v2 = {"name":"John", "age":36, "gender":"Male"}.keys()
print(v1, v2) # ['name', 'age'] gender
print(*v1, v2) # name age gender
* can get only the values from a dictionary.
*v1, v2 = {"name":"John", "age":36, "gender":"Male"}.values()
print(v1, v2) # ['John', 36] Male
print(*v1, v2) # John 36 Male
* can get both the keys and values from a dictionary.
*v1, v2 = {"name":"John", "age":36, "gender":"Male"}.items()
print(v1, v2)
# [('name', 'John'), ('age', 36)] ('gender', 'Male')
print(*v1, v2)
# ('name', 'John') ('age', 36) ('gender', 'Male')
print(v1[0], v1[1], v2[0], v2[1])
# ('name', 'John') ('age', 36) gender Male
print(*v1[0], *v1[1], v2[0], v2[1])
# name John age 36 gender Male
v1, v2, *v3 = "Hello"
print(v1, v2, v3) # H e ['l', 'l', 'o']
print(v1, v2, *v3) # H e l l o
*Again, zero or more *iterables can be passed to a function with the zero or more values unpacked from zero or more iterables.
print(*[0, 1, 2])
print(*(0, 1, 2))
print(*range(3))
# 0 1 2
print(*'Hello') # H e l l o
print([[0, 1, 2], 'Hello']) # [[0, 1, 2], 'Hello']
print(*[[0, 1, 2], 'Hello']) # [0, 1, 2] Hello
print([*[0, 1, 2], *'Hello']) # [0, 1, 2, 'H', 'e', 'l', 'l', 'o']
print(*[*[0, 1, 2], *'Hello']) # 0 1 2 H e l l o